This invention relates to coupling agent compositions comprising a conventional silane coupling agent and a bis(trialkoxysilyl)organo compound, and partially hydrolyzed products of such mixtures. These coupling agent compositions can also be used as primers in the production of laminates and other composite materials.
Conventional silane coupling agents are well known in the plastic forming and composite materials arts for bonding resins to fillers and substrates. Typically as part of the process of producing composite materials, reinforcing fillers are treated with silane coupling agents before being introduced into the uncured resin. The silane coupling agents form a coating on the filler, and the coating interacts with the resin, either chemically or through the formation of interpenetrating polymer networks, to form a strong cohesive bond between the resin and filler. A significant benefit of silane coupling agents is the added hydrolytic stability they provide composite materials.
The particular silane coupling agent which will produce the strongest and most hydrolytically stable composite material depends upon the resin used in said composite. Ordinarily, the silane coupling agent is chosen based upon the functionality of the nonhydrolyzable group attached to the silane, however, some silanes are effective coupling agents with resins even where the silane is relatively unreactive with the resin used in the composite. Recommendations for choosing the most effective coupling agent for a particular filler/resin combination are present in the art.
The performance and cost of silane coupling agents, while adequate, can be improved by the addition of further chemical compounds. U.S. Pat. No. 3,816,152, issued to P. C. Yates June 11, 1974, teaches the addition of silicic and polysilicic acid to organofunctional silanes to lower the cost of coupling agent compositions. While these compositions are effective coupling agents, they do not in all cases provide composites as strong as composites made with organofunctional silane coupling agents alone. Thus, a coupling agent composition more effective than the organofunctional silane alone would be useful in the plastic forming arts.